Polymers having a polyisocyanurate structure are known for their high thermal stability and flame resistance. Polyisocyanurate-containing foams (PUR/PIR-foams) based on aromatic 4,4′-diphenylmethane diisocyanate (MDI) and polyether polyols and polyepoxides are widely used on account of their very low thermal conductivity for example, in particular as high-performance insulating materials.
Polyisocyanurates also find practical application as crosslinking agents in paint chemistry, the production of which involves stopping the trimerization reaction at low conversions and removing excess unreacted monomeric diisocyanate. Thus, in the production of crosslinking agents based on isocyanurates proceeding from aliphatic and mixed aliphatic and aromatic monomeric diisocyanates, DE 31 00 263; GB 952 931, GB 966 338; U.S. Pat. No. 3,211,703 or 3,330,828 envisage performing the reaction either in dilute conditions or only up to low conversion values with very precise temperature control. Crosslinked polyisocyanurate plastics materials are specifically not formed, only oligomeric, low-viscosity, soluble products. U.S. Pat. No. 6,133,397 discloses a coating composition having a low content of volatile organic compounds and a viscosity (ZAHN-cup 2) of less than about 200 seconds. The composition consists essentially of at least one aliphatic polyisocyanate, a solvent in an amount between 0% and 45% based on the weight of the polyisocyanate in the composition, and a trimerization catalyst. The composition is essentially free from volatile mono- and diisocyanates.
Isocyanurates constructed based on isocyanates having an NCO functionality of more than two retain free NCO groups which may be further functionalized by subsequent reactions.
EP 0 000 658 A1 discloses a process for producing an ethylenically unsaturated isocyanurate in which a polyisocyanate is reacted with a hydroxyl component containing a monohydric alcohol, wherein said isocyanurate contains a vinylidene group but no allyl group, wherein the reaction is performed in the presence of a copper salt to obtain an isocyanate-containing urethane, wherein the amounts of the hydroxyl component and the polyisocyanate are chosen such that after said reaction 0.75 to 1.6 mol of unconverted isocyanate groups per mole of polyisocyanate used are retained. Subsequently, a catalytic amount of an isocyanate trimerization catalyst which initiates trimerization of the isocyanate-containing urethane without causing gelation is added so that the isocyanate-containing urethane is timerized to produce an ethylenically unsaturated isocyanurate. In one embodiment the monohydric alcohol may be hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, or a mixture thereof.
EP 0 315 020 A2 relates to a process for producing compounds comprising isocyanurate groups and olefinic double bonds by reaction of a) a polyisocyanate component comprising isocyanurate groups and containing polyisocyanates with b) an olefinically unsaturated alcohol component consisting of at least one hydroxyalkyl ester of acrylic acid or methacrylic acid, characterized in that one uses a) as the polyisocyanate component (i) N,N′,N″-tris(isocyanatohexyl) isocyanurate present optionally in admixture with its higher homologues comprising more than one isocyanurate ring or (ii) mixtures of the polyisocyanates recited under (i) with up to 40 NCO equivalent % based on the entirety of component a) of other polyisocyanates with aliphatically and/or cycloaliphatically bonded isocyanate groups, and the reaction is performed with co-use of c) a polyol component consisting essentially of a polyester polyol having an OH number of 80 to 350 based on (i) acid component consisting to an extent of at least 80 carboxyl equivalent % of adipic acid and/or isophthalic acid and (ii) a polyol component consisting at least to an extent of 70 hydroxyl equivalent % of 1,6-hexanediol, wherein the amount of component c) makes up 20 to 150 wt % based on the weight of component b) and the reaction is performed while maintaining an NCO/OH equivalent ratio of 0.9:1 to 1.1:1, wherein the alcoholic components b) and c) are reacted with the polyisocyanate component in any desired sequence or in admixture. In one embodiment 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate or any desired mixtures of these compounds are used as component b).
EP 0 347 610 A2 describes UV-curable mixtures containing A) 15-60 wt % based on the total of 100 wt % of A)+B)+C) of reaction products of hydroxyalkyl acrylates with aliphatic polyisocyanates containing at least 2 isocyanate groups and at least one uretdione and/or triisocyanurate and/or biuret group per molecule; B) 30-84 wt % based on the total of 100 wt % of A)+B)+C) of di- or trifunctional (meth)acrylates having a molecular weight below 500; C) 1-10 wt % based on the total of 100 wt % of A)+B)+C) of compounds having one polymerizable group per molecule and a molecular weight below 200, and D) photoinitiators in customary amounts based on the total of 100 wt % of A)+B)+C). In the mixtures component A) may represent reaction products of hydroxyethyl acrylate with the uretdione and/or triisocyanurate and/or biuret based on hexamethylene diisocyanate.
U.S. Pat. No. 4,145,544 discloses a process for producing an ethylenically unsaturated isocyanurate comprising the steps of (1) trimerization of an aromatic polyisocyanate to form an NCO-containing isocyanurate, wherein the trimerization is performed in the presence of an isocyanate trimerization catalyst and a solvent; and (2) reaction of the NCO groups present in the NCO-containing isocyanurate with the hydroxyl group of a monohydric alcohol containing a vinylidene group in the presence of a solvent to form an ethylenically unsaturated isocyanurate. The solvent employed in steps (1) and (2) is a vinylidene solvent which is free from groups that react with isocyanate groups and which contains at least 20 weight % of an ethylenically unsaturated polar solvent. In one embodiment the monohydric alcohol is hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate or mixtures thereof.
U.S. Pat. No. 4,159,376 relates to a process for producing an ethylenically unsaturated isocyanurate, comprising a first step of reacting an aromatic polyisocyanate with a monohydric alcohol containing a vinylidene group selected from hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate or mixtures thereof to form a monoisocyanate-containing urethane, and comprising a second step of reacting the monoisocyanate-containing urethane with tris(2-hydroxyethyl)isocyanurate to obtain an ethylenically unsaturated isocyanurate.